1. Technical Field
The present invention generally relates to an automotive air conditioning system and, more particularly, to an air intake for an automotive air conditioning system.
2. Description of the Prior Art
FIG. 1 illustrates a prior art automotive air conditioning system generally designated by the numeral 10. Air conditioning system 10 includes duct 12 which defines an air passage 13. The forward (or left as illustrated in FIG. 1) portion of duct 12 is a closed end formed by the gradual narrowing of duct 12. Outside air intake 14 and first passenger compartment air intake (first air intake) 15 are formed adjacent to the closed end of duct 12. Outside air intake 14 admits air from outside the automobile passenger compartment to duct 12. First air intake 15 admits air from the passenger compartment to duct 12. First damper 16 is disposed within duct 12. First damper 16 selectively controls the opening and closing of outside air intake 14 and first air intake 15 in response to air conditioning demand. Air conditioning demand may, for example, be determined by the setting of temperature control switches by a vehicle passenger. Blower 17 forces air from the forward to the rear (or right as illustrated in FIG. 1) portion of duct 12 and is positioned within air passage 13. Evaporator 18 and heater core 19 are disposed within air passage 13 and are positioned rearwardly of blower 17. First opening 111, second opening 112, and third opening 113 are formed at the rear portion of duct 12. First opening 111 directs blown air to defrost an automobile windshield (not shown). Second opening 112 directs blown air to the lower portion of footspace of the automobile passenger compartment. Third opening 113 directs blown air to the upper portion of the automobile passenger compartment.
Second passenger compartment air intake (second air intake) 20 is formed in a wall portion of duct 12 between first air intake 15 and blower 17. Second damper 21 is disposed within duct 12 and is adjacent to second air intake 20. Second damper 21 is a dead load-type damper, i.e., second damper 21 closes second passenger compartment air intake 20 by virtue of its weight. However, when air flows in duct 12, damper 21 is subjected to a force tending to counter the dead-load weight. When the speed of blown air in duct 12 exceeds a predetermined value, second air intake 20 is opened due to the movement of second damper 21, as illustrated in FIG. 1. Thus, second air intake 20 admits additional air from the passenger compartment to duct 12.
When blower 17 is operated, outside air or air from the passenger compartment is admitted to duct 12 depending on the position of first damper 16. the air flows through evaporation 18 and heater core 19 and is heated or cooled in response to the desired temperature of the passenger compartment. Finally, the air is directed through first opening 11, and/or second opening 112, and/or third opening 113. When the speed of the blown air in duct 12 exceeds a predetermined value, additional air from the passenger compartment is admitted to duct 12 through second passenger compartment air intake 20 and joins the above-described air flow. Thus, air from the passenger compartment may be admitted to duct 12 even if first damper 16 is positioned to admit only outside air.
The circulation of air from the passenger compartment through duct 12 is not always desired. For example, it is sometimes desirable to heat the passenger compartment utilizing only outside air so as to provide fresh air and comfortable ventilation to the passenger compartment. Thus, both first air intake 15 and second air intake 20 should be closed, i.e., only outside air should be admitted to duct 12. However, in the above-described prior art system, second air intake 20 cannot be forced to remain closed since second damper 21 is a dead load type damper. Accordingly, heating of the passenger compartment with comfortable ventilation and fresh, outside air is obtained ineffectively.